The City of Belfast Dog Training Club meets in a community centre in the Castlereagh Hills. At 27 years old, Tracey Douglas is the youngest of the trainers. She sets the scene. "If you see, there's a wee kitchen. Kathryn Adair would be there, waiting to greet people, saying, 'Ooh, you're for the puppy class.' She was always very warm, very welcoming."

Suzanne Cassells is a bright and brisk redhead in her early 30s. She helps Tracey run the last training session of the evening. "Some nights can be challenging, but Kathryn was always there to reassure you," she says. It is more than 18 months since Adair's conviction for fraud, and still everyone feels a profound sense of disbelief. "She was the face and the heart of the club," Suzanne says. Alex Douglas, 53, is Tracey's father and chair of the club. "We've had so long to think about it," he says, "but even now I wonder, did she just befriend us all to do this? Or were we good friends first? Were we being groomed?"

The members of the City of Belfast Dog Training Club are lucky in being part of a close community. Liz Young is in her 40s, the owner of a local dog-walking business. Following an operation on a sarcoma, she has a dressing on her face, which makes her self-conscious. She sounds apologetic. "When it all came out, I was actually a bit relieved that there were other people involved." Discovering they were in the same boat helped soften the feelings of vulnerability and shame. Sharing information also helped bring Adair to justice. Ted (not his real name) is in his early 60s, a senior committee member and the longest-serving trainer at the club. Ted did more than anyone to help build the case against Adair, yet he does not want to be identified: "I prefer to remain anonymous, and goodness knows how many unknown ones there are, suffering in silence."

Adair with her Bernese mountain dog Benson, in 2005.

Adair was 36 when she first visited the club in 2003 with her cousin Jill. "Her cousin had come to train a jack russell," Tracey tells me. "Then one day Kathryn came with her big, beautiful Bernese mountain dog." The dog, Benson, soon became a club favourite, always found lying in a corner while Adair busied herself offering tea and biscuits. "A lot of dogs can get hyper around children, but Benson let the kids pet him," Suzanne says. Bernese mountain dogs are big, almost the size of a St Bernard. In pictures, they are often seen pulling carts filled with smiling children. Benson became something of a local celebrity. His brown and white face appears, open-mouthed, on the label of Brandy dog food. Benson died at the age of nine, which is old for a Bernese.

Was the dog Adair's secret weapon? If Benson was so well-loved, did that blind people to Adair's lies and schemes? Not one person accepts the idea. Adair was Adair, I'm told. She was special. "She was the face and the heart of the club," Suzanne says.

"I think it all started over the dog," Alex says. "But we don't know that. We can trust nothing."

Alex lives in an ordinary semi on a street near Stormont. The moment I touch the bell, the dogs begin barking. Tracey answers the door with her Australian shepherd, a kind of outsized, fluffy collie, but the barking continues until I am safely inside the house. I find out why when I peer through the curtains to the back. There are 16 labradors in a compact series of kennel runs, entirely filling the small garden. "If you keep looking, they'll keep barking," Tracey tells me. The moment the curtains close, the dogs fall silent, but a strong smell lingers. Next to the window is a portrait of a labrador signed by Adair. "Kathryn was an excellent artist," Tracey says. Alex is a respected labrador breeder. It was his experience as a breeder that led to his introduction to Benson.

The Castlereagh Hills lie to the south-east of Belfast. There is no real centre, just endless housing developments. Alex used to drive for a living. In the past, he has driven President Clinton's security detail, Janet Jackson and Norman Wisdom. He has a relaxed, reassuring way as he takes me on a tour. As the road curves away, there are glimpsed views down to the harbour or to the lopsided brick of the Black Mountain. Kathryn Adair grew up in an area named Four Winds at the highest point of Castlereagh. It is well named. The wind is biting cold on a December afternoon. Alex points out the neat, 1960s house where Kathryn lived with her widowed mother, Meta. According to Kathryn, when her mother died in 2007, she inherited the house and her brother, Colin – a manager for the Ulster Bank, like his late father, Tom – inherited cash. Alex remembers Meta fondly. He met her in 2002, a little before Kathryn joined the club. A woman he knew hoped to mate her bitch with Benson, and Alex came to help. The attempt was unsuccessful.

It was Adair's next attempt to breed Benson, in 2005, that ended in disaster. "That's the story, anyway," Alex says. "It's supposedly where all her own money went." He recounts the tale as Adair told it to him. "There were seven pups born, and four survived, though they became ill. For some reason, they were taken to a vet in Newry, and from there to another clinic across the border. Kathryn was handing out thousands to help pay the fees, because she felt sorry for them, she said." Adair told the club she ended up spending £18,000, saving just two of the puppies. Now that he knows more about Adair, Alex is sceptical about the story.

Tracey Douglas at her dog grooming shop. Photograph: Rob Durston for the Guardian

In autumn 2010, the City of Belfast Dog Training Club held its annual general meeting and discussed options for the £8,000 the club had built up over 20 years. Adair was a member of the committee. She waited a week, then appealed for emergency funds, though not in person. "She had spoken to Alex," Tracey says, "but she couldn't face speaking to everyone as a group, as I remember. So Alex put it to the committee for her, because she was too scared to talk to people, so upset and stuff."

I speak to the committee members in the room used for the weekly training sessions, gathered in a circle on plastic stacking chairs. Daphne (not her real name) was the club treasurer at the time. She would hate to be identified, she says; not everyone in her family knows the story, even now. She bent over backwards to spare Adair's feelings. "When I put the loan through, I said to Alex, 'We are letting everyone know Kathryn's business. So we'll put it down as something else.' We put it through – may God forgive me – as a deposit on savings." As she speaks, she begins to cry. She remembers Adair borrowed £5,600 and asked for it to be delivered in cash to Belfast bus station. "She had been up in Ballycastle and I met her on Glengall Street and handed over the money and it was, thank you very much, thank you very much, and all the rest of it," Daphne says. "And then, a while after that, she was looking for about £1,200."

Adair needed money as a result of a family feud. Or so she claimed. Daphne shakes her head: "She only told us that. We don't know." The money was to pay taxes, to release her mother's money from an offshore bank. I wonder that a story of feuds and secret bank accounts never raised suspicion? "You have to appreciate the trust that Kathryn had," Alex says. "She could have told you the sky was pink and you would have believed her."

Club photos show a tall woman with short blond hair and a ready smile. Adair is pictured receiving a gift-wrapped package from Alex on her 40th birthday. She poses at the club's annual summer show in a red anorak with a big Bernese dog badge on her breast. Other pictures from local magazines and charity prospectuses show Adair with local Brownies, donating books to schools. Or working with the SOS Bus, a charity that helps vulnerable youngsters on Belfast's streets. Or attending the Ulster People of the Year Award with fellow charity workers. This is the Adair who was loved and respected by everyone at the club. She had endless time for others, though Tracey now wonders that she was quick to change the subject if anyone strayed too close to questions about her own feelings. She was tireless and selfless, and seemed uninterested in money. "There was no sign of that sort of thing," one member says, a sentiment echoed by Liz Young. "She insisted the money meant nothing to her."

Daphne says, "The third time she came up to us for about £2,300 and Alex came to me and said, 'What have we got?' I said, 'We could do her for about £900.' But I had money in my house, so I could make it up. Alex said, 'Are you sure?' And I said, 'Yes.' At that time, my husband had gone into hospital. He had cancer. He was in hospital 12 days and he died."

People who love dogs share a connection that overcomes differences of age and education. This is what Alex, Daphne, Tracey and Suzanne share, not much else, but it is a deep bond. Adair must have felt secure. She was not content to borrow just from the club; she also approached individual members, swearing each one to secrecy. Liz says, "She told me I was the only one she would ever trust." This brings nods from around the room: everyone was told the same line. No one is wealthy. But they are careful people, natural savers. Plus Adair seemed to have a gift for appearing on doorsteps just when people might have a little extra. Daphne continued to lend her money, using her late husband's life policy. Adair ultimately took her for a little short of £20,000. Alex gave her £5,000 after being made redundant. Another club member received insurance money on the death of his father. His wife had already lent Adair several thousand, he says, "So when she came round to talk about the money she owed us, I was ready to rip her head off. But at the end of it I'm sitting and writing her a cheque, and I'm happy to do it."

At her trial, Adair returned to the story of Benson's pups and the struggle to save their lives. It is unusual for the stud owner to pay vet fees in such circumstances. Adair had told the club she felt sorry for the pups, but at her trial she gave a different account. She said the owner of the bitch pressured her to pay the fees. Over the years, however, they remained in contact and several years later he supplied her with a new Bernese mountain dog, Finlay, a grandchild of Benson's from one of his surviving daughters. He also seems to have continued to ask Adair for money. In court, this shadowy Bernese breeder was referred to only as Mr A. The man was questioned by the police but never charged, nor publicly identified. But in Adair's account, he was the real crook.

"She tried to say she was a stupid wee girl," Liz says. Alex agrees: "She tried to plead naivety, of not being streetwise. But the judge saw through that. She was too well educated." The fact that both her father and brother were bank managers became a factor in her trial, as did her grammar school education and her degree in fine art. She was a talented artist who raffled vouchers at the club's summer show that could be redeemed for one of her famous pet portraits.

As Alex grew worried about the club's money and his own redundancy cheque, Adair sought to reassure him. He believes he spoke to Mr A. "I had a few calls from a guy claiming to be a financial adviser, though you could never get him when you wanted him. He would speak just long enough to confirm, 'Yes, Kathryn is one of our clients, oh sorry, I've got to go now, I'm just being called into court.'" Ted tells the same story. "I spoke to him. Or I spoke to a person. But when you phoned the number, morning, lunchtime, whenever, you never got an answer. It was a pay-as-you-go mobile that was turned off and only used to call you."

Alex, Ted and Daphne finally compared stories and discovered Adair had borrowed £40,000 from the club and its members. As they approached the annual summer dog show in July 2011, Alex and Daphne confronted Adair at her home. They saw no sign that she was enjoying the money. The house was cold. The kitchen seemed bare. Daphne remembers: "She was in floods of tears. Alex had driven us up, and as we left, I said, 'She'll be all right, she won't do anything daft?' Because, honestly, we were worried."

The annual dog show held on the Billy Neill fields in Castlereagh is one of the key events in Northern Ireland's dog calendar. Liz had not visited the club in several years, but went to the show to find Adair, who was proving hard to reach. She wasn't there. "And then I found that you all wanted to speak to her as well," Liz says. "When I saw the look on everyone's faces, I didn't have to say anything." Liz had lent Adair £17,500. It was Liz and Ted who pushed the club to go to the police. When the day came, Alex joined them. Liz says, "I spoke to a friend in the police, and she spoke to her dad who was in the fraud squad, and they arranged that we went down to Musgrave Street." This is Belfast's central police station. "They said, don't just go down to your local police station, because they won't do anything about it. They'll say it's like a loan or something like that. So we went down to speak to someone in the fraud squad."

It was only when the club considered bringing bankruptcy proceedings that a solicitor's search discovered Adair's cousin, Alora McMullan, had already initiated proceedings a year earlier. But in December 2010 the McMullans were suddenly repaid. It turned out that Adair's brother had forestalled the bankruptcy by remortgaging his mother's old house, repaying the McMullans and, it transpired, Adair's work colleagues. When Ted learned this, he went to speak to Victor Corbett, who owned the newsagent's where Adair worked. "So I went up, knock, knock. And his wife is saying, 'He's not here for the minute.' So I say, 'Perhaps I can talk to you?' And she says, 'It's about Kathryn Adair, isn't it? She's doing more people.' Or some line like that." By remortgaging the house, the Adairs paid a total of £63,000 back to Kathryn's victims. The news that she had continued taking money prompted Victor to put Ted in touch with another neighbour from the Four Winds. "That was how I met Liz McFarland," Ted says. "So that's how we knew the width of it."

Adair's house in Four Winds has been sold. A quarter of a mile down the road is a strip mall of low-rise shop units in front of a parking lot. The first shop is empty but still has a sign indicating it was once Corbett's Newsagent. Adair worked behind the counter at Corbett's, and when the shop closed, she moved to the Mace supermarket three doors down. Adair started in the newsagent's at 15 years old. Despite three A-levels, a degree and her family's banking tradition, she was still working for the Corbetts in her 40s. Alex parks in front of the Mace, still open late in the evening. I search out the packs of Brandy dog food and take a look at what I assume is Benson's face, though it may be Finlay – he took over the Brandy job when his grandfather died.

Liz McFarland is a small vigorous woman, a widow of just two years. Many of Adair's victims prefer not to be identified, but Liz no longer cares. "My Brian's gone now, so it doesn't matter." Liz had known Adair for 30 years, but she thought of her as a loner, in sharp contrast to the dedicated charity worker who posed for photographs in the newspapers, or the bubbly woman of the dog club. "Kathryn never had any friends," Liz says. "She just went about with her mother to these art exhibitions, which is how I met her. She got my husband into exhibiting his paintings."

Liz McFarland lent Adair £7,000. ‘She came back a week later and I lent her another £6,000.’ Photograph: Rob Durston for the Guardian

Following her old strategy, Adair appeared at Liz's door when Brian was ill. She chatted with the couple for two and a half hours, but it was only when she was alone with Liz that she began crying. "I asked her what it was about and she said she needed money." Adair took £7,000. "Then she came back a week later and I lent her another six. And I hadn't told my husband. Then, at the end of the month, she phoned me: she wanted another seven something. This time I did tell my husband. I said I'd loaned her the six. He said, 'What, hundred?' I said, 'No, thousand.' And he lost his reason. So I never told him about the rest."

Liz joined forces with the dog club. They built a website, stopthefourwindsfraudster.com, but the police told them they could not use it, nor could they distribute the flyers they had printed. "A few posters might have made a huge difference to the number of people that came forward," Ted says. Nevertheless, they tracked down another dozen victims ready to make statements, bringing the total to 18. The sums involved were far higher than anyone had imagined.

In two years, Adair had taken in excess of a quarter of a million pounds. She had gone out of her way to target older people and the bereaved. But the story that she had fallen out with her brother's family seemed wide of the mark. In court, at least, they came to support her each day. Her old grammar school headteacher and even her ex-employer gave character statements. At that point, the club members hit a low. "You could see by Kathryn's face in court that she thought she was getting off," one says. In his summing up, the judge commented that the charges were specimen. No one doubts there were more victims. A few, at least, had died. If Adair had persisted in her plea of not guilty, she would have received five years in prison. On the last day of the trial, however, she changed her plea and was sentenced to three years and told she could expect to serve 18 months.

The City of Belfast Dog Training Club welcomed the sentence. The judge took time to read their victim statements, and he delivered a verdict that club members felt reflected the gravity of Adair's crimes. The sense of relief is palpable. At the same time, however, everyone still feels they are short of answers. Why did Adair target them? In her last month in prison, Adair wrote to the club members, but they are disappointed with the apology. "It was a boilerplate letter with no feelings whatsoever," Ted says.

Adair was declared bankrupt in prison. The final settlement was 5.2p in the pound, meaning that Alex got something over £270, Liz Young got a little over £900. There is speculation that if Adair's family had not hushed up the first round of frauds, she would have been stopped earlier. There are more conspiratorial rumours, too. Might the money be stashed in bin bags in a loft somewhere? One club member says, darkly, "Knowing the way things are over here, that amount of money doesn't disappear without it turning up somewhere else."

The members of the dog club find it hard to accept that upwards of a quarter of a million pounds was blown in two years by a man who struck up a relationship with a lonely, unmarried woman who lived for her dogs. Some believe that Adair may have been in thrall to her renegade Bernese breeder, yet all of them see her as the brains, the manipulator who picked out each of her victims, returning to them until they were bled dry. Liz McFarland says, "The day she was arrested, she took £3,000 off the wee barber in Newton Park. He met her that morning and she was arrested at 4.30 that afternoon. She wrecked his business, and the rumour is that he borrowed it off people who would have wanted their money back pronto. So he had to close the shop and run."

Adair was recently seen out walking Finlay. The stories she told continue to reverberate through the Castlereagh Hills, breeding suspicion and fresh rumours. Adair is a shadowy figure; her motives are unclear. She made her victims meet her in car parks, garage forecourts and bus stations, and again and again she walked away with envelopes full of money. The City of Belfast Dog Training Club worked together to bring Kathryn Adair to justice. But it doesn't feel like a victory. Adair was once the heart and soul of their club. Perhaps it is just the effect of a cold winter night in Castlereagh, but sitting with the members in the hall, it feels as though the heart is broken.